Known in the art is an acoustic wave element having a piezoelectric substrate and an excitation electrode provided on the major surface of the piezoelectric substrate. Such an acoustic wave element is for example utilized for a reception filter (Rx filter) or transmission filter (Tx filter) of a branching filter.
Here, in the branching filter, when the interval between the Tx band and the Rx band is narrow, since the frequency ends up moving due to a change of the ambient temperature (−30° C. to +85° C.), it was difficult to satisfy the transmittance property and attenuation property which are required for the Tx band and Rx band. As a technique for solving this, there is the technique of using a temperature-compensated piezoelectric substrate (see Japanese Patent Publication No. 2007-214902A etc.)